A hybrid vehicle may include an engine, an electric machine, and a step ratio transmission. The transmission allows different vehicle speeds to be achieved while allowing the engine to operate in a desired speed range. By operating the engine in a desired speed range, engine emissions and performance may be improved. However, consistently shifting gears of a step ratio transmission as a vehicle ages may require on-going adaptation of transmission control parameters. Vehicle occupants may find it objectionable to wait for vehicle parameters to be adapted when they wish to reach a destination. Further, since internal combustion piston engines combust at fixed crankshaft intervals, it may be difficult to decouple combustion artifacts from the parameter or variable being adapted. Therefore, it would be desirable to provide a way of adapting transmission control parameters with minimal vehicle occupant interference.
The inventors herein have recognized the above-mentioned issues and have developed a powertrain operating method, comprising: at least partially engaging a gear synchronizer or a band brake while rotating a transmission input shaft via an electric machine, a transmission output shaft held stopped while rotating the transmission input shaft via the electric machine; and adjusting transmission shifting in response to a torque transferred via the gear synchronizer or the band.
By rotating transmission components via an electric machine and adjusting transmission shifting responsive to torque transferred while a transmission output shaft is held stopped, it may be possible to determine operating status of transmission components. In one example, a transmission component state may be adjusted while an electric machine rotates an input shaft of a transmission while the output shaft of the transmission is not rotating. The change in electric machine current may be indicative of torque transferred via the transmission shift element. The shift element state may be adjusted while the vehicle is parked or stopped during a drive cycle so that vehicle occupants may not be disturbed. In still other examples, vehicle speed may be maintained while transmission parameters are determined so that transmission control parameters may be adjusted with a lower possibility of disturbing vehicle occupants.
The present description may provide several advantages. In particular, the approach may improve transmission operation over a life of a transmission. Further, the approach may improve transmission operation without disturbing vehicle occupants. In addition, the approach may provide improved control parameter estimates.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.